1. Field of the Invention
The present invention relates to a high-frequency dielectric ceramic composition and electronic devices using the same.
2. Description of the Related Art
Dielectric ceramics are widely used as materials for a dielectric resonator, a dielectric filter, a circuit board, etc., which are mounted on electronic apparatuses used in a high-frequency region such as a microwave or millimeter wave region, or the like, such as a cellular telephone, personal communication equipment, satellite broadcasting receiver, etc.
Dielectric characteristics required for such high-frequency dielectric ceramics include (1) a high dielectric constant (.di-elect cons..sub.r) for complying with the need for miniaturization because the wavelength of electromagnetic waves is shortened to 1/(.di-elect cons..sub.r).sup.1/2 in the dielectric material, (2) a low dielectric loss, i.e., a high Q value, (3) excellent temperature stability of resonance frequency, i.e., the temperature coefficient (.tau.f) of the resonance frequency of about 0 ppm/.degree. C., etc.
Examples of conventional known dielectric ceramic compositions include dielectric ceramic compositions such as Ba(Zn, Ta)O.sub.3 system compositions (Japanese Patent Publication No. Sho-58-25068), Ba(Sn, Mg, Ta)O.sub.3 system compositions (Japanese Patent Publication No. Hei-3-34164), (Zr, Sn)TiO.sub.4 system compositions (Japanese Patent Publication No. Hei-4-59267), Ba.sub.2 Ti.sub.9 O.sub.20 (Japanese Laid-open Patent Application No. Sho-61-10806).
However, Ba(Zn, Ta)O.sub.3 based and Ba(Sn, Mg, Ta)O.sub.3 based materials have a high Q value of 150,000 to 300,000 (at 1 GHz) but have a relatively low dielectric constant (.di-elect cons..sub.r) of 24 to 30.
On the other hand, (Zr, Sn)TiO.sub.4 based materials and Ba.sub.2 TiO.sub.20 have a relatively high dielectric constant (.di-elect cons..sub.r) of 37 to 40, and a high Q value of 50,000 to 60,000 (at 1 GHz), but it is difficult to realize a relatively high dielectric constant (.di-elect cons..sub.r) of over 40.
There has recently been increasing demand for decreasing the loss and miniaturizing electronic apparatus, and accordingly, there has been increasing demand for developing dielectric materials having excellent dielectric characteristics, particularly, both a high dielectric constant (.di-elect cons..sub.r) and a high Q value. However, at present, it is impossible to satisfactorily comply with these demands.